diff --git a/README.md b/README.md
index 8b187ef..e814e06 100644
--- a/README.md
+++ b/README.md
@@ -222,6 +222,8 @@ public class Main {
         .build();
 
     try {
+      // A workspace id is required: pass it here (new DecisionModel("your-workspace-id"))
+      // or set the DASHSCOPE_WORKSPACE environment variable before running.
       DecisionModel decisionModel = new DecisionModel();
       DecisionModelResult result = decisionModel.call(param);
       System.out.println(JsonUtils.toJson(result));
@@ -232,4 +234,8 @@ public class Main {
 }
 ```
 
-The `call` method accepts a `DecisionModelParam`, and returns a `DecisionModelResult` whose `answers` are keyed by question id. Streaming is not supported. The API key is read from the `DASHSCOPE_API_KEY` environment variable by default, or set explicitly with `apiKey(...)`; the request url defaults to `https://maas.qianwenaiapi.com/compatible-mode/v1/systemone`, override it with `new DecisionModel(baseUrl)` or the `DASHSCOPE_HTTP_BASE_URL` environment variable.
+The `call` method accepts a `DecisionModelParam`, and returns a `DecisionModelResult` whose `answers` are keyed by question id. Streaming is not supported. The API key is read from the `DASHSCOPE_API_KEY` environment variable by default, or set explicitly with `apiKey(...)`.
+
+The endpoint is workspace-scoped: the base URL is composed as `https://{workspace}.{region}.maas.aliyuncs.com/compatible-mode/v1` (the `systemone` path is appended automatically). A workspace id is **required** — pass it to the constructor (`new DecisionModel(workspace)` or `new DecisionModel(workspace, region)`) or set the `DASHSCOPE_WORKSPACE` environment variable; otherwise constructing the client throws `IllegalArgumentException`. The region defaults to `cn-beijing` and can be set via `DASHSCOPE_API_REGION`.
+
+To target a fully custom endpoint (for example the Token Plan gateway), use the static factory `DecisionModel.withBaseUrl(baseUrl)`. Note that `new DecisionModel(String)` treats its argument as a **workspace id**, not a base URL. You can also override the entire base URL with the `DASHSCOPE_DECISION_BASE_URL` environment variable; the SDK-wide `DASHSCOPE_HTTP_BASE_URL` is intentionally not read here.
diff --git a/README_zh.md b/README_zh.md
index 43a1741..a552caf 100644
--- a/README_zh.md
+++ b/README_zh.md
@@ -222,6 +222,8 @@ public class Main {
         .build();
 
     try {
+      // 必须提供 workspace：可在此传入（new DecisionModel("你的-workspace-id")），
+      // 或在运行前设置 DASHSCOPE_WORKSPACE 环境变量。
       DecisionModel decisionModel = new DecisionModel();
       DecisionModelResult result = decisionModel.call(param);
       System.out.println(JsonUtils.toJson(result));
@@ -232,4 +234,8 @@ public class Main {
 }
 ```
 
-`call` 方法接受 `DecisionModelParam`，并返回 `DecisionModelResult`，其中 `answers` 按问题 id 给出答案，不支持流式输出。API Key 默认从环境变量 `DASHSCOPE_API_KEY` 获取，也可以通过 `apiKey(...)` 指定；请求地址默认为 `https://maas.qianwenaiapi.com/compatible-mode/v1/systemone`，可通过 `new DecisionModel(baseUrl)` 或环境变量 `DASHSCOPE_HTTP_BASE_URL` 覆盖。
\ No newline at end of file
+`call` 方法接受 `DecisionModelParam`，并返回 `DecisionModelResult`，其中 `answers` 按问题 id 给出答案，不支持流式输出。API Key 默认从环境变量 `DASHSCOPE_API_KEY` 获取，也可以通过 `apiKey(...)` 指定。
+
+请求地址是 workspace 作用域的：base URL 由 `https://{workspace}.{region}.maas.aliyuncs.com/compatible-mode/v1` 拼接而成（`systemone` 路径会自动追加）。**必须**提供 workspace id——通过构造函数传入（`new DecisionModel(workspace)` 或 `new DecisionModel(workspace, region)`），或设置环境变量 `DASHSCOPE_WORKSPACE`；否则构造客户端时会抛出 `IllegalArgumentException`。region 默认为 `cn-beijing`，可通过环境变量 `DASHSCOPE_API_REGION` 设置。
+
+若要指向完全自定义的端点（例如 Token Plan 网关），请使用静态工厂方法 `DecisionModel.withBaseUrl(baseUrl)`。注意 `new DecisionModel(String)` 会把参数当作 **workspace id**，而不是 base URL。你也可以用环境变量 `DASHSCOPE_DECISION_BASE_URL` 覆盖整个 base URL；此处的实现有意不读取全局的 `DASHSCOPE_HTTP_BASE_URL`。
\ No newline at end of file
diff --git a/samples/DecisionModelUsage.java b/samples/DecisionModelUsage.java
index 2a289cd..31c14cc 100644
--- a/samples/DecisionModelUsage.java
+++ b/samples/DecisionModelUsage.java
@@ -40,6 +40,9 @@ public static void main(String[] args) throws Exception {
             .questions(questions)
             .build();
 
+    // A workspace id is required: pass it here (new DecisionModel("your-workspace-id"))
+    // or set the DASHSCOPE_WORKSPACE environment variable before running.
+    // For a fully custom endpoint, use DecisionModel.withBaseUrl(baseUrl) instead.
     DecisionModel decisionModel = new DecisionModel();
     DecisionModelResult result = decisionModel.call(param);
     System.out.println(JsonUtils.toJson(result));
diff --git a/src/main/java/com/alibaba/dashscope/aigc/imagesynthesis/ImageSynthesis.java b/src/main/java/com/alibaba/dashscope/aigc/imagesynthesis/ImageSynthesis.java
index 68256bb..ecdd908 100644
--- a/src/main/java/com/alibaba/dashscope/aigc/imagesynthesis/ImageSynthesis.java
+++ b/src/main/java/com/alibaba/dashscope/aigc/imagesynthesis/ImageSynthesis.java
@@ -33,6 +33,30 @@ public static class Models {
     public static final String WANX_2_1_IMAGEEDIT = "wanx2.1-imageedit";
   }
 
+  /**
+   * Model prefixes that are only served on the multimodal-generation endpoint. The legacy
+   * text2image endpoint used by this class rejects them with a 400 "url error", so they must be
+   * called through {@link com.alibaba.dashscope.aigc.imagegeneration.ImageGeneration} instead.
+   */
+  private static final String[] MULTIMODAL_MODEL_PREFIXES = {"wan2.6-t2i", "wan2.6-image"};
+
+  private static void checkMultimodalModel(String model) {
+    if (model == null) {
+      return;
+    }
+    for (String prefix : MULTIMODAL_MODEL_PREFIXES) {
+      if (model.startsWith(prefix)) {
+        throw new IllegalArgumentException(
+            String.format(
+                "Model '%s' is only served on the multimodal-generation endpoint and is not "
+                    + "supported by ImageSynthesis. Use "
+                    + "com.alibaba.dashscope.aigc.imagegeneration.ImageGeneration "
+                    + "(ImageGeneration.call/asyncCall/streamCall) for this model.",
+                model));
+      }
+    }
+  }
+
   /** Image edit function */
   public static class ImageEditFunction {
     public static final String STYLIZATION_ALL = "stylization_all";
@@ -112,6 +136,7 @@ public ImageSynthesis(String task, String baseUrl) {
 
   public ImageSynthesisResult asyncCall(ImageSynthesisParam param)
       throws ApiException, NoApiKeyException {
+    checkMultimodalModel(param.getModel());
     // add local file support
     try {
       param.checkAndUpload();
@@ -126,11 +151,15 @@ public ImageSynthesisResult asyncCall(ImageSynthesisParam param)
   }
 
   /**
-   * Note: This method currently now only supports wan2.2-t2i-flash and wan2.2-t2i-plus. Using other
-   * models will result in an error，More raw image models may be added for use later
+   * Synchronously generate images on the legacy text2image endpoint.
+   *
+   * <p>Multimodal-generation models (wan2.6-t2i / wan2.6-image) are not served here; use {@link
+   * com.alibaba.dashscope.aigc.imagegeneration.ImageGeneration#call} for those. Calling this method
+   * with such a model throws {@link IllegalArgumentException}.
    */
   public ImageSynthesisResult syncCall(ImageSynthesisParam param)
       throws ApiException, NoApiKeyException {
+    checkMultimodalModel(param.getModel());
     // add local file support
     try {
       param.checkAndUpload();
@@ -152,6 +181,7 @@ public ImageSynthesisResult syncCall(ImageSynthesisParam param)
    */
   public ImageSynthesisResult call(ImageSynthesisParam param)
       throws ApiException, NoApiKeyException {
+    checkMultimodalModel(param.getModel());
     // add local file support
     try {
       param.checkAndUpload();
diff --git a/src/test/java/com/alibaba/dashscope/TestImageSynthesis.java b/src/test/java/com/alibaba/dashscope/TestImageSynthesis.java
index 7741cea..a6d3bfe 100644
--- a/src/test/java/com/alibaba/dashscope/TestImageSynthesis.java
+++ b/src/test/java/com/alibaba/dashscope/TestImageSynthesis.java
@@ -201,4 +201,20 @@ public void testImageSynthesisWithPromptExtendAndWatermark()
     assertEquals(true, requestBody.contains("\"prompt_extend\":true"));
     assertEquals(true, requestBody.contains("\"watermark\":false"));
   }
+
+  @Test
+  public void testSyncCallRejectsMultimodalModel() {
+    int port = server.getPort();
+    Constants.baseHttpApiUrl = String.format("http://127.0.0.1:%s", port);
+    ImageSynthesis is = new ImageSynthesis();
+    ImageSynthesisParam param =
+        ImageSynthesisParam.builder().model("wan2.6-t2i").prompt("a cat").build();
+    IllegalArgumentException ex =
+        org.junit.jupiter.api.Assertions.assertThrows(
+            IllegalArgumentException.class, () -> is.syncCall(param));
+    org.junit.jupiter.api.Assertions.assertTrue(
+        ex.getMessage().contains("ImageGeneration"), ex.getMessage());
+    // no request should have reached the legacy endpoint
+    assertEquals(0, server.getRequestCount());
+  }
 }